Physical vapor deposition (PVD) is a well-known process for depositing a thin film of material on a substrate and is commonly used in the fabrication of semiconductor devices. The PVD process is carried out at high vacuum in a chamber containing a substrate (e.g., wafer) and a solid source or slab of the material to be deposited on the substrate, i.e., a PVD target. In the PVD process, the PVD target is physically converted from a solid into a vapor. The vapor of the target material is transported from the PVD target to the substrate where it is condensed on the substrate as a thin film.
There are many methods for accomplishing PVD including evaporation, e-beam evaporation, plasma spray deposition, and sputtering. Presently, sputtering is the most frequently used method for accomplishing PVD. During sputtering, gas plasma is created in the chamber and directed to the PVD target. The plasma physically dislodges or erodes (sputters) atoms or molecules from the reaction surface of the PVD target into a vapor of the target material, as a result of collision with high-energy particles (ions) of the plasma. The vapor of sputtered atoms or molecules of the target material is transported to the substrate through a region of reduced pressure and condenses on the substrate, forming the thin film of the target material.
PVD targets have finite service lifetimes. PVD target overuse, i.e., use beyond the PVD target's service lifetime, raises reliability and safety concerns. For example, PVD target overuse can result in perforation of the PVD target and system arcing. This, in turn, may result in significant production losses, PVD system or tool damage and safety problems.